The satisfactory removal of greasy soils/stains, that is soils/stains having a high proportion of triglycerides or fatty acids, is a challenge faced by the formulator of detergent compositions for use in laundry and dish washing methods. Surfactant components have traditionally been employed in detergent products to facilitate the removal of such greasy soils/stains. In particular, surfactant systems comprising cationic esters have been described for use in greasy soil/stain removal.
A challenge faced in laundry and dish washing is not just the removal of greasy soils and stains from the soiled/stained substrate, but dispersion of the greasy stain/soil components, thereby preventing their (re)deposition onto the substrates. Grease dispersing agents can be employed in detergents to achieve prevention of (re)deposition of greasy stains/soils. Examples of grease dispersing agents are polymers with hydrophobic side chains and hydrophilic monomer units in the backbone.
EP-B-21,491 discloses detergent compositions containing a nonionic/cationic surfactant mixture and a builder mixture comprising aluminosilicate and polycarboxylate builder. The cationic surfactant may be a cationic ester. Improved particulate and greasy/oily soil removal is described.
U.S. Pat. No. 4,228,042 discloses biodegradable cationic surfactants, including cationic ester surfactants for use in detergent compositions to provide greasy/oily soil removal. The combination of these cationic surfactants with nonionic surfactants in compositions designed for particulate soil removal is also described.
U.S. Pat. No. 4,260,529 discloses laundry detergent compositions having a pH of no greater than 11 containing cationic ester surfactant and nonionic surfactant at defined weight ratios.
WO 91/08281 discloses dispersing polymers for dispersion of detergent droplets, with a hydrophilic backbone and hydrophobic side chains.
It has now been found that the performance of certain grease dispersing agents in the traditional detergents is affected by the washing conditions, such as water hardness. Essential for the performance of grease dispersing agents is their affinity for and absorbance onto the (greasy) stain/soil components on the fabric. However, absorbance onto the stained fabric can be problematic when `limesoaps` (formed by the alkali and earth alkali metals of the water hardness with fatty acids) are present on the fabric. This problem is believed to cause the reduced performance of the dispersing agents.
The Applicants have now found that this problem can be ameliorated by the inclusion of cationic ester surfactants in detergents containing grease dispersing agents, which are polymers with a hydrophilic backbone and hydrophobic side chain(s). Detergent compositions employing both components have shown to deliver a surprisingly better cleaning performance.
Two mechanisms are believed to be responsible for these benefits. Firstly, the cationic ester surfactant is can reduce deposition of `lime soaps` on the fabric. The reduction of deposition will facilitate the absorbance of the grease dispersing agent onto the greasy soils or stains. Thereby, an improvement of their dispersing performance is achieved. Secondly, it is believed that the cationic ester surfactant can act to facilitate solubilisation of greasy soil/stain components. This will aid the grease dispersing agent's dispersal of the soil/stain components. Thus, an overall improved cleaning of the detergent is achieved.
All documents cited in the present description are, in relevant part, incorporated herein by reference.